Domestic heating systems generally involve a unit that is euphemistically described as a boiler, and which may be wall mounted or self-standing. It is generally the central unit of the heating system, and the output is generally hot water that is used either indirectly for heating a hot water circuit (for hot water dispensed from taps and showers), usually referred to as DHW, and directly, for space, or central, heating of the building in which the boiler is located, usually referred to as CH. Of course, direct supply of DHW is also possible in “combi” arrangements.
The source of power for such boilers may be gas or another fuel or another source.
Increasingly there is a demand for local electricity generation and the economics of such generation are beginning to make sense. WO-A-2003/014534 describes an integrated micro combined heat and power (CHP) system, in which a conventional boiler is provided with a steam circuit that provides heat to an organic rankine cycle (ORC) machine that employs a scroll as the expander, the scroll driving a generator to generate electricity. The present invention relates especially, although not exclusively, to such an arrangement.
However, there are also other potential capabilities required of a boiler such as provision within the appliance of a thermal store, or of an air conditioning unit, for example. Also, it is desirable to render boilers adaptable.
WO-A-2010/061190 discloses a boiler unit housed in an enclosure configured to receive a solid state combined heat and power unit or a rankine or stirling engine (CHP device), wherein the boiler unit comprises a heat generating device and a control unit to independently control the heat generating device and the CHP device, wherein the boiler unit is operable without the CHP device being present.
GB-A-2376271 discloses a similar arrangement.